Among fluorine-containing elastomers, a fluorine-containing elastomer containing a vinylidene fluoride unit (VdF) has been widely used because of its excellent heat resistance, chemical resistance, solvent resistance and fuel oil resistance in the fields such as automobile industry, semiconductor industry and chemical industry by forming into shapes such as O-rings, hoses, stem seals, shaft seals and diaphragms. Conventionally, a fluorine-containing elastomer containing a vinylidene fluoride unit (VdF) has been generally applied to a technique of crosslinking reaction with peroxide (see, e.g., JP-A-53-125491) and a technique of crosslinking reaction with polyol (see, e.g. JP-B-53-4035 and JP-A-6-128334).
However, required properties become severer along with advance in technology, in the aerospace field, the semiconductor manufacturing apparatus field, the chemical plant field and the automobile industry, sealing property in a high temperature environment exceeding 200° C. has been required, and it is difficult to meet the requirement sufficiently with the conventional molded articles and the sealing materials obtained by peroxide crosslinking and polyol crosslinking.
On the other hand, for the required properties under such a high temperature environment, it has been proposed that heat resistance is tried to be improved by devising a crosslinking system. For example, using a fluorine-containing elastomer in which cyano groups are introduced as a crosslinking point, a triazine crosslinking system in which triazine rings are formed by an organic tin compound (see, e.g., JP-A-58-152041); in the same manner, using a fluorine-containing elastomer in which cyano groups are introduced as a crosslinking point, an oxazole crosslinking system in which oxazole rings are formed by a bisaminophenol; an imidazole crosslinking system in which imidazole rings are formed by a bisdiaminophenyl compound (see, e.g., JP-A-59-109546); a thiazole crosslinking system in which thiazole rings are formed by bisaminothiophenol (see, e.g. JP-A-8-104789); and a composition comprising a fluorine-containing elastomer having a carboxylic group as a crosslinking point at the terminal of the main chain and/or in a branched chain, and an oxazole crosslinking agent, an imidazole crosslinking agent or a thiazole crosslinking agent (see, e.g., WO 00/29479 pamphlet).
However, as a fluorine-containing elastomer used in Examples of each proposal, it is only a perfluoroelastomer, in a non-perfluoroelastomer containing vinylidene fluoride, there was no fluorine-containing elastomer composition obtained by carrying out the above-described oxazole crosslinking, imidazole crosslinking or thiazole crosslinking, which is excellent in compression permanent strain at high temperature.
The present invention provides a fluorine-containing elastomer composition capable of crosslinking reaction, comprising a fluorine-containing elastomer containing a vinylidene fluoride unit, which is excellent in heat resistance, and a compound containing at least two crosslinking reaction groups. Also, the present invention provides a molded article excellent in heat resistance and a sealing material for an oxygen sensors, which are obtained by crosslinking the fluorine-containing elastomer composition.